Method of producing leaky coaxial cable

Abstract

A method of producing a leakage graded coaxial cable having a braided shield, in which ends of the shield wire are dropped as braiding progresses. Gaps in the shield having progressively increasing size are produced through which the radio frequency field leakage occurs, which facilitates providing a constant radio frequency field around the cable. The cable is coated with a jell flooding agent prior to extrusion of its protection jacket, which fills the interstices and gaps of the shield, and solidifies to a waxy, semi-resilient consistency. The resulting cable can be coiled and flexed, maintaining its shield reliability, and rejects water and fluids in case pinholes in the jacket occur.

We claim: 
     
       1. A method of making a leaky coaxial cable comprising: (a) preparing a conductive axial wire covered by an insulating dielectric,   (b) progressively braiding a conductive braid shield around the dielectric, and   (c) dropping ends of the braid according to a predefined schedule for successive lengths of the braid shield, to produce progressively larger gaps in the braid shield as the ends are dropped whereby graded leakage of signal carried by the cable is facilitated.   
     
     
       2. A method as defined in claim 1 including the further steps of covering the braid with a flooding agent, covering the flooded braid with an insulating protective jacket, and causing the flooding agent to solidify. 
     
     
       3. A method as defined in claim 1 or 2, including braiding insulative fillers in the braid in place of the dropped ends. 
     
     
       4. A method as defined in claim 2 wherein the protective jacket is polyethylene. 
     
     
       5. A method as defined in claim 1, 2 or 4, including the step of changing the number of ends per carrier for successive lengths of the cable according to a predetermined schedule to vary the area of the gaps. 
     
     
       6. A method as defined in claim 1, 2 or 4 including the steps of changing the number of ends per carrier and of varying the angle of the ends of the shield for successive lengths of the cable according to a predefined schedule to vary the configuration and area of the gaps. 
     
     
       7. A method of making a coaxial cable comprising: (a) progressively drawing a conductive axial wire covered by a cellular polyethylene insulating dielectric through a shield braiding machine,   (b) braiding a conductive wire shield around the dielectric using wire ends supplied from a plurality of bobbins carried on the machine,   (c) cutting wire ends from predetermined ones of the bobbins,   (d) braiding the shield using the same lay angle and continuing with the same braiding schedule, but without the cut ends, while continuing to draw the dielectric and shield covered wire through the machine,   whereby gaps in the shield braid along the cable are produced.   
     
     
       8. A method as defined in claim 7, including: (a) heating a meltable flooding agent to a liquid consistency in a bath container,   (b) drawing the shield covered wire through the bath container whereby the flooding agent fills interstices within the cable,   (c) drawing a protective jacket over the flooded cable, and   (d) cooling the cable, thus solidifying the jacket and the flooding agent to a gell.   
     
     
       9. A method of making a leaky coaxial cable comprising: (a) preparing a conductive axial wire covered by an insulating dielectric,   (b) progressively braiding a conductive braid shield around the dielectric,   (c) dropping ends of the braid according to a predefined schedule for successive lengths of the braid shield, and   (d) braiding insulative fillers in the braid in place of the dropped braid ends,   whereby progressively larger gaps in the braid shield filled by insulated fillers are produced as the ends are dropped and graded leakage of signal carried by the cable is facilitated.   
     
     
       10. A method as defined in claim 9 including the further steps of covering the braid with a flooding agent, covering the flooded braid with an insulating protective jacket, and causing the flooding agent to solidify. 
     
     
       11. A method as defined in claim 10, including braiding insulative fillers in the braid in place of the dropped ends. 
     
     
       12. A method as defined in claim 10 wherein the protective jacket is polyethylene. 
     
     
       13. A method as defined in claim 10, including the step fo changing the number of ends per carrier for successive lengths of the cable according to a predertermined schedule to vary the area of the gaps. 
     
     
       14. A method as defined in claim 10, including the steps of changing the number of ends per carrier and of varying the angle of the ends of the shield for successive lengths of the cable according to a predefined schedule to vary the configuration and area of the gaps.